1. Field of the Invention
The present invention pertains to wireless telecommunications, and particularly to roaming of a mobile user equipment unit (UE).
2. Related Art and other Considerations
In a typical cellular radio system, mobile user equipment units (UEs) communicate via a radio access network (RAN) to one or more core networks. The user equipment units (UEs) can be mobile stations such as mobile telephones (“cellular” telephones) and laptops with mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified, typically by a unique identity, which is broadcast in the cell. The base stations communicate over the air interface (e.g., radio frequencies) with the user equipment units (UE) within range of the base stations. In the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
One example of a radio access network is the Universal Mobile Telecommunications (UMTS) Terrestrial Radio Access Network (UTRAN). The UTRAN is a third generation system which is in some respects builds upon the radio access technology known as Global System for Mobile communications (GSM) developed in Europe. UTRAN is essentially a wideband code division multiple access (W-CDMA) system. An endeavor know as the Third Generation Partnership Project (3GPP) is seeking to evolve yet further the UTRAN.
As those skilled in the art appreciate, in W-CDMA technology a common frequency band allows simultaneous communication between a user equipment unit (UE) and plural base stations. Signals occupying the common frequency band are discriminated at the receiving station through spread spectrum CDMA waveform properties based on the use of a high speed code, such as a pseudo-noise (PN) code. These high speed PN codes are used to modulate signals transmitted from the base stations and the user equipment units (UEs). Transmitter stations using different PN codes (or a PN code offset in time) produce signals that can be separately demodulated at a receiving station. The high speed PN modulation also allows the receiving station to advantageously generate a received signal from a single transmitting station by combining several distinct propagation paths of the transmitted signal. In CDMA, therefore, a user equipment unit (UE) need not switch frequency when handoff of a connection is made from one cell to another. As a result, a destination cell can support a connection to a user equipment unit (UE) at the same time the origination cell continues to service the connection. Since the user equipment unit (UE) is always communicating through at least one cell during handover, there is no disruption to the call. Hence, the term “soft handover.” In contrast to hard handover, soft handover is a “make-before-break” switching operation.
The radio network controller (RNC) controls the UTRAN. In fulfilling its control role, the RNC manages resources of the UTRAN. Such resources managed by the RNC include (among others) the downlink (DL) power transmitted by the base stations; the uplink (UL) interference perceived by the base stations; and the hardware situated at the base stations.
There are several interfaces of interest in the UTRAN. The interface between the radio network controllers (RNCs) and the core network(s) is termed the “Iu” interface. The interface between a radio network controller (RNC) and its base stations (BSs) is termed the “lub” interface. The interface between the user equipment unit (UE) and the base stations is known as the “air interface” or the “radio interface” or “Uu interface”. In some instances, a radio connection involves both a Serving or Source RNC (SRNC) and a target or drift RNC (DRNC), with the SRNC controlling the radio connection but with one or more radio links of the radio connection being handling by the DRNC. An interface between radio network controllers (e.g., between a Serving RNC [SRNC] and a Drift RNC [DRNC]) is termed the “Iur” interface, and can be realized (for example) by an Inter-RNC transport link.
Those skilled in the art appreciate that, with respect to a certain RAN-UE connection, an RNC can either have the role of a serving RNC (SRNC) or the role of a drift RNC (DRNC). If an RNC is a serving RNC (SRNC), the RNC is in charge of the radio connection with the user equipment unit (UE), e.g., it has full control of the radio connection within the radio access network (RAN). A serving RNC (SRNC) is connected to the core network. On the other hand, if an RNC is a drift RNC (DRNC), its supports the serving RNC (SRNC) by supplying radio resources (within the cells controlled by the drift RNC (DRNC)) needed for the radio connection with the user equipment unit (UE). A system which includes the drift radio network controller (DRNC) and the base stations controlled over the Iub Interface by the drift radio network controller (DRNC) is herein referenced as a DRNC subsystem or DRNS.
When a radio connection between the radio access network (RAN) and user equipment unit (UE) is being established, the radio access network (RAN) decides which RNC is to be the serving RNC (SRNC) and, if needed, which RNC is to be a drift RNC (DRNC). Normally, the RNC that controls the cell where the user equipment unit (UE) is located when the radio connection is first established is initially selected as the serving RNC (SRNC). As the user equipment unit (UE) moves, the radio connection is maintained even though the user equipment unit (UE) may move into a new cell, possibly even a new cell controlled by another RNC. That other RNC becomes a drift RNCs (DRNC) for RAN-UE connection. An RNC is said to be the Controlling RNC (CRNC) for the base stations connected to it by an Iub interface. This CRNC role is not UE specific. The CRNC is, among other things, responsible for handling radio resource management for the cells in the base stations connected to it by the Iub interface.
In certain situations it its advantageous to transfer control of a particular UE connection from one RNC to another RNC. Such a transfer of control of the UE connection from one RNC to another RNC has been referred to as soft RNC handover, SRNC moveover, and SRNC relocation. A relocate function/procedure is provided to effect this transfer of control. This is a general function/procedure covering UMTS internal relocations (e.g., relocation of SNRC within the UMTS) as well as relocations to other systems (e.g., from UMTS to GSM, for example). SRNC relocation is described in various references, including the following example commonly assigned patent applications (all of which are incorporated herein by reference):
(1) U.S. patent application Ser. No. 09/035,821 filed Mar. 6, 1998, entitled “Telecommunications Inter-Exchange Measurement Transfer”;
(2) U.S. Pat. No. 6,233,222 entitled “Telecommunications Inter-Exchange Congestion Control”;
(3) U.S. Pat. No. 6,246,878 entitled “Multistage Diversity Handling For CDMA Mobile Telecommunications”;
(4) U.S. Pat. No. 6,230,013 entitled “Diversity Handling Moveover For CDMA Mobile Telecommunications”;
(5) U.S. patent application Ser. No. 09/732,877 filed Dec. 11, 2000, entitled “Control Node Handover In Radio Access Network”;
(6) U.S. patent application Ser. No. 09/543,536 filed Apr. 5, 2000, entitled “Relocation of Serving Radio Network Controller With Signaling of Linking of Dedicated Transport Channels”.
(7) U.S. patent application Ser. No. 09/829,001 filed Apr. 10, 2001, entitled “Connection Handling in SRNC Relocation”.
SRNC relocation is intended to make more efficient use of the transmission network. Once the former SRNC is not needed, the connection to the core network is moved and the connection between the two RNCs (the former SRNC and the former DRNC over the Inter-RNC link) is disconnected.
For each mobile that the SRNC is serving, the SRNC stores a bit string which permanently identifies the mobile. According to the RAN system specified by the Third Generation Partnership Project (3GPP), this bit string is the IMSI, and is transferred to the SRNC from the CN using a Common ID procedure over the Iu interface at connection establishment. In the 3GPP approach, the structure of the IMSI is not recognized or used by the SRNC. It is only used to coordinate a paging from one CN domain with a connection that is ongoing for the other CN domain (matching two bit strings). The CRNC stores cell information for all cells which it controls.
Currently the Third Generation Partnership Project (3GPP) envisions some cooperation between mobile network operators. It may be, for example, that two (or more) operators each have their respective operator networks (e.g., a public mobile network network [PLMN]), and are cooperating in some parts of the coverage area (e.g. rural areas) but are competing in other areas (e.g. city areas). In the 3GPP parlance, the two networks are defined as “equivalent PLMNs” with regards to the cell selection process in a mobile terminal. This equivalence for cell selection enables the terminal to select cells of networks other than the operator's network to which the mobile terminal subscribes.
For example, as illustrated in FIG. 1, a network of a first operator may have cells (illustrated by solid line circles in FIG. 1) serving or covering primarily a northern half of the country (e.g. above line L in FIG. 1), while a network of a second operator may have cells (illustrated by dotted line circles in FIG. 1) serving or covering primarily a southern half of the country (e.g., below line L. in FIG. 1). Further, both the first operator and the second operator may serve a competition area (e.g., city) framed by line C in FIG. 1 (e.g., both operators have cells in the city/metropolitan area). The first and second operator should cooperate at least to the extent that the mobile terminal of a subscriber of the first operator who travels out of the first operator's network (e.g., below line L) should be able to establish mobile communication using the cells of the second operator, and vise versa.
Importantly, one of the operators (such as the first operator) may not wish for the mobile terminal subscribing to the other operator's network to use cells (e.g., of the first operator) in a region where the two operators have competing cells. For example, the first operator in FIG. 1 may not desire for a mobile terminal (UE), which subscribes to the subscription operators' network (e.g., the second operator's network in the case of FIG. 1) to use a cell of the first operator's network when the UE moves into the competition area C. Given the smaller cell size of the first operator's (solid line) cells in the competition area C of FIG. 1, and the greater number of cells provided by the first operator in the competition area C, the first operator likely may have invested considerably more in radio access network infrastructure that the second operator, providing better signal reception, traffic capacity, or coverage than the second operator. For these or other reasons, the first operator may wish to preclude the mobile terminal (which subscribes to the competing second operator's network) from using the (possibly superior) cells of the first operator, particularly since the second operator has provided competing cells in the same area.
For idle mode mobile terminals, the concept of “forbidden LA” (e.g., forbidden location area) results in rejection of access. When a mobile terminal is informed that a certain location area (LA) is forbidden, the mobile terminal has to find another LA (and will eventually select its own PLMN). Moreover, the mobile terminal also stores a list of forbidden LA which is used to avoid selecting a forbidden LA in the future when the mobile terminal is in its idle mode.
Whereas access rejection is currently feasible for idle mode mobile terminals, presently there is no way to stop connected mode terminals belonging to a competitor's network from accessing cells in another network. What can happen, therefore, is that (in the competition area) a first operator may invest extensively to provide quality coverage, while the competing second operator may try to save money by providing poorer coverage, since the subscribers of the second operator's network can still reuse the coverage of the other first operator's network. Such considerations undermine both effective competition and cooperation.
What is needed, therefore, and an object of the present invention, is a technique for precluding or rejecting accesses, in competition areas, to cells of a first operator's network attempted by or on behalf of a mobile terminal which subscribes to a second operator's network.